Process and apparatus for manufacturing tyres for vehicle wheels

ABSTRACT

A carcass ply is built on a forming drum by application of a plurality of strip-like elements by the steps of: setting a width of these strip-like elements, setting a width of the overlapped part between two adjacent strip-like elements, setting a fitting diameter of the forming drum by calculating a corresponding extension of a radially external laying surface, and calculating a whole number of strip-like elements to be applied. The whole number of drip-like elements is applied by rotating the forming drum around a geometric rotation axis thereof, and applying pairs of strip-like elements by means of a first laying unit and a second laying unit located close to opposite portions of the forming drum relative to the geometric rotation axis. When the calculated whole number of strip-like elements is an odd number, before at least one application step, the first laying unit is shifted along an adjustment path orthogonal to the geometric rotation axis and substantially tangent to the radially external laying surface of the forming drum.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 13/960,414, filedAug. 6, 2013, which is a division of application Ser. No. 12/744,880,filed May 26, 2010, which is a national phase application based onPCT/IB2007/054875, filed Nov. 30, 2007, the content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process and an apparatus formanufacturing tyres for vehicle wheels.

The present invention further relates to a method of building at leastone carcass ply during manufacture of a tyre for vehicle wheels.

In more detail, the invention is particularly directed to the processand equipment that, during building of a green tyre, are used for thepurpose of manufacturing carcass plies.

2. Description of the Related Art

A tyre for vehicle wheels generally comprises a carcass structureincluding at least one carcass ply having respectively opposite endflaps in engagement with respective annular anchoring structuresintegrated into the regions usually identified with the name of “beads”,and having an inner diameter substantially corresponding to a so-called“fitting diameter” of the tyre on a respective mounting rim.

Associated with the carcass structure is a belt structure comprising oneor more belt layers, disposed in radially superposed relationship withrespect to each other and to the carcass ply and having textile ormetallic reinforcing cords with a crossed orientation and/orsubstantially parallel to the circumferential extension direction of thetyre. A tread band is applied at a radially external position to thebelt structure, the tread band too being made of elastomeric materiallike other semifinished products constituting the tyre.

Respective sidewalls of elastomeric material are also applied at anaxially external position to the side surfaces of the carcass structure,each extending from one of the side edges of the tread band until closeto the respective annular anchoring structure to the beads. In tyres ofthe tubeless type an airtight coating layer, usually identified as“liner,” covers the inner surfaces of the tyre.

Subsequently to building of the green tyre obtained through assembly ofrespective components, a vulcanisation and moulding treatment isgenerally carried out, said treatment aiming at causing structural,stabilisation of the tyre by cross-linking of the elastomeric compounds,as well as at impressing it with a desired tread pattern and withpossible distinctive graphic signs at the tyre sidewalls.

The carcass structure and belt structure are generally made separatelyfrom each other in respective work stations to be mutually assembled ata second time.

In more detail, manufacture of the carcass structure first involvesapplication of the carcass ply or plies onto a building drum.Subsequently the annular anchoring structures to the beads are fitted orformed on the opposite end flaps of the carcass ply or plies and areafterwards turned up around the annular structures themselves so as toencompass them in a sort of loop to form a so-called substantiallycylindrical “carcass sleeve”. In the most widespread productionprocesses, the carcass plies are made starting from an article ofmanufacture in the form of a continuous strip, formed of cords oftextile, or in some cases metallic, material, disposed parallel to eachother in a matrix of elastomeric material. Then a segment of a lengthcorresponding to the circumferential extension of the carcass ply to beobtained is cut from said continuous strip. The segment is wound up onthe outer surface of a building drum and the opposite ends thereof arejoined together to form a carcass ply.

At the same time, a so-called “outer sleeve” is made on a second drum orauxiliary drum, which sleeve comprises the belt layers applied inradially superposed relationship with respect to each other, andpossibly the tread band applied at a radially external position to thebelt layers. The outer sleeve is then picked up from the auxiliary drumto be coupled with the carcass sleeve. To this aim, the outer sleeve iscoaxially disposed around the carcass sleeve and then the carcass ply orplies are shaped into a toroidal configuration by axially approachingthe beads to each other and simultaneously admitting fluid underpressure into the carcass sleeve, so as to give rise to radial expansionof the carcass plies until causing adhesion of same against the innersurface of the outer sleeve.

Assembly of the carcass sleeve to the outer sleeve can be carried out onthe same drum as used for manufacturing the carcass sleeve, in whichcase the process is referred to as a “unistage building process”.

Also known are building processes of the so-called “two-stage type” inwhich a so-called “first-stage drum” is used to make the carcass sleeve,while assembly between carcass structure and outer sleeve is carried outon a so-called “second-stage drum” or “shaping drum” onto which thecarcass sleeve picked up from the first-stage drum and subsequently theouter sleeve picked up from the auxiliary drum are transferred.

To the aims of the present specification and the following claims, by“strip-like element” it is intended an elongated article of manufacturehaving a cross-section profile with a flattened conformation andcomprising one or more cords of textile and/or metallic material,extending parallel to the longitudinal extension of the strip-likeelement itself and embedded into, or at least partly coated with, atleast one layer of elastomeric material.

Document E0928680 in the name of the same Applicant, shows that thecarcass plies are made of strip-like elements formed with rubberisedcords, laid down in circumferential mutually approached relationship onthe outer surface of a toroidal forming support substantially conformingin shape to the inner conformation of the tyre being manufactured. Oneor more belt layers are subsequently formed by means of respectivestrip-like elements laid down in circumferential mutually approachedrelationship on the carcass ply or plies carried by the toroidal formingsupport.

Document WO01/38077 in the name of the same Applicant, shows that a beltstructure is made of thread segments each comprising parallel cordsembedded into an elastomeric layer and sequentially laid incircumferential mutually approached relationship on a toroidal support.During laying of each segment, an angular rotation of the toroidalsupport is determined around a correction axis radial to the rotationaxis of the toroidal support itself, located at a substantiallybarycentric position relative to the segment that is about to be laid.

SUMMARY OF THE INVENTION

The Applicant has noticed that the same type of strip-like elementsshown in EP0928680 or WO01/38077 can be used for manufacturing tyres inthe previously-described apparatuses of the unistage or two-stage types,in which the carcass sleeve is submitted to radial expansion untilmaking it adhere against the inner surface of the outer sleeve.

The Applicant has felt the necessity to make carcass structures fortyres through laying of strip-like elements using laying cycles quickenough to enable this step to be carried out in high-productivityapparatuses for tyre manufacture.

The Applicant has therefore noticed that by laying the strip-likeelements on a forming drum (of a substantially cylindrical shape) in aneven number and two by two, by means of the laying units located atsubstantially opposite portions of the drum relative to the rotationaxis of the drum itself, the time of a work cycle necessary to make eachply and therefore each carcass structure can be reduced.

The Applicant has further felt the necessity to make carcass structuresfor tyres on the same apparatus, by laying strip-like elements forproducing tyres with different sizes.

In this regard, the Applicant has observed that the outercircumferential extension of the building drum used for building eachcarcass ply must correspond to a multiple integer of the pitch betweentwo strip-like elements in succession.

This pitch, if the strip-like elements are disposed close to each other,corresponds to an arc of a circumference subtended by each strip-likeelement on the surface of the drum itself.

If the strip-like elements partly overlap each other, the pitchcorresponds to the arc of a circumference subtended by each strip-likeelement to which the width of the overlapped part must be subtracted,i.e. the mutual-overlapping length between two adjacent strip-likeelements measured along the circumferential extension of the drum.

The Applicant has observed that this condition is at least affected bythe width size of the strip-like elements being employed and by thelaying angle of same on the forming drum surface, as well as by thewidth of the overlapped part that must have values within predeterminedranges, and by the circumferential extension of the drum itself which islinked to the fitting diameter of the tyre.

The Applicant has also observed that with use of strip-like elementshaving a few millimetre width, a width included between 3 mm and 5 mmfor example, and controlling the amount of the overlapped part between astrip-like element and the subsequent one, the above described solutionin order to ensure building of tyres different from each other at eachcycle, by use of two laying units, could always be employed becausemanagement of an in any case even number of strip-like elements to belaid on the forming drum, by varying the width of the overlapped part,is of easy accomplishment.

However the Applicant has noticed that use of strip-like elements havinga moderate cross width inevitably gives rise to longer building timeseven with use of the above described laying units.

The Applicant has seen that this problem can be solved with use ofstrip-like elements having a width in the order of one or more tens of amillimetre. In this case however, for some tyre sizes, it could not bepossible to control, by means of said overlapped parts, the space takenup by a single “odd” strip-like element resulting from division of thecircumference of the forming support by the width of the strip-likeelements themselves. Since empty spaces cannot be left, in particulardue to the subsequent shaping step briefly described above, that in thiscase would produce unacceptable unevennesses, one strip-like element isto be compulsorily added in order to come back to an even number, but inthis case the overlapped parts between the strip-like elements becomeexcessive and have repercussions on the quality of the finished product.

The Applicant has further, noticed that solving the above mentionedproblems by use of a specific drum for each size and type of tyre to bemade, which drum has to be then combined with specific equipment adaptedto manufacture the strip-like elements of suitable width, would beuneconomic.

The Applicant has therefore felt the necessity to make carcassstructures for tyres through laying of strip-like elements without beingobliged to be submitted to the above described constraints.

The Applicant has realised that by planning the laying units in such amanner that at least one of them has at least one degree of freedomrelative to the laying surface of the strip-like elements makes itpossible, in case of need, to lay single strip-like elements too(therefore with a total odd number of them) in order to solve the abovementioned problems relating to the production speed and flexibility inan efficient and cheap manner.

More specifically, the Applicant has found that by adjusting theposition of at least one of the two laying units along an arced path oftravel about the radially external laying surface, a whole number ofstrip-like elements can be laid down, so that the design specificationscan be always observed.

In accordance with a first aspect, the invention relates to a method ofbuilding at least one carcass ply during manufacture of a” tyre, saidcarcass ply being built by laying an odd whole number of strip-likeelements on a radially external surface exhibited by a forming drum,said method comprising the steps of:

-   -   rotating the forming drum around a geometric rotation axis        thereof;    -   applying said strip-like elements through a first laying unit        and a second laying unit located close to opposite portions of        said forming drum relative to the geometric rotation axis;

wherein, before at least one application step, the first laying unit issubmitted to shifting along an adjustment path that lies in a planeorthogonal to the geometric rotation axis and is substantially arcedabout the radially external laying surface of the forming drum.

In more detail, in accordance with a second aspect, the inventionrelates to a process for manufacturing tyres for vehicle wheels, eachtyre comprising a carcass structure, a tread band at a radially externalposition to said carcass structure and a belt structure interposedbetween said carcass structure and tread band, wherein the step ofbuilding the carcass structure comprises at least the steps of:

-   -   building at least one carcass ply on a forming drum around at        least one radially external laying surface by application of a        plurality of strip-like elements, said at least one carcass ply        having axially opposite end flaps;    -   coaxially engaging an annular anchoring structure around each of        the end flaps; wherein the step of building said at least one        carcass ply comprises at least the steps of:    -   setting a fitting diameter of the forming drum;    -   setting a radial thickness of components of the tyre present on        the forming drum before the step of building said at least one        carcass ply;    -   calculating a corresponding extension of the radially external        laying surface;    -   setting a width W of said strip-like elements;    -   setting a width of the overlapped part S between two adjacent        strip-like elements; —setting a ply angle γ;    -   calculating a whole number of strip-like elements to be applied;    -   applying the calculated whole number of strip-like elements by        rotating the forming drum around a geometric rotation axis        thereof, and applying said strip-like elements through a first        laying unit and a second laying unit located close to opposite        portions of said forming drum relative to the geometric rotation        axis;

wherein, when the calculated whole number of strip-like elements is anodd number, before at least one application step, the first laying unitis submitted to shifting along an adjustment path that lies in a planeorthogonal to the geometric rotation axis and is substantially arcedabout the radially external laying surface of the forming drum.

Thus, more production flexibility is advantageously given to the plantsfor building tyres. In fact, it is the Applicant's opinion that, giventhe circumferential extension of the radially external surface exhibitedby the drum resulting from the fitting diameter of the tyre and from thetire components already present on the drum itself, given the width ofthe strip-like elements, given the ply angle and given a design width ofthe overlapped part, adjustment of the position of one of the layingunits enables an even or odd whole number of strip-like elements to belaid down, of such a value that the true width of the overlapped partalways keeps within a predetermined and acceptable range.

In addition, by the invention it is possible to use sufficiently widestrip-like elements so that their number along the circumferentialextension of the drum can be contained within limits, as well as thetime of the work cycle.

In accordance with a further aspect, the invention relates to anapparatus for manufacturing tyres for vehicle wheels, each tyrecomprising a carcass structure, a tread band at a radially externalposition to said carcass structure, and a belt structure interposedbetween said carcass structure and tread band, said apparatuscomprising:

-   -   a forming drum having at least one radially external laying        surface;    -   devices for building at least one carcass ply around said        radially external surface, said at least one carcass ply having        axially opposite end flaps;    -   devices for coaxially engaging an annular anchoring structure        around each of the end flaps; wherein the devices for building        at least one carcass ply around said radially external surface        comprise:    -   devices for setting the forming drum in rotation around a        geometric rotation axis thereof;    -   a first laying unit and a second laying unit mounted to mutually        opposite portions of the forming drum and adapted to apply a        plurality of strip-like elements along the circumferential        extension of the forming drum;    -   an adjustment device for shifting the first laying unit along an        adjustment path that lies in a plane orthogonal to the geometric        rotation axis and is substantially arced about said radially        external laying surface for applying a single strip-like        element.

The present invention, in at least one of said aspects, can have one ormore of the preferred features hereinafter described.

Preferably, the angular measure of said shifting corresponds to theangular measure in a transverse direction either of said strip-likeelement laid down on said forming drum or of a fraction thereof.

Said shifting is of such a nature as to create, during the laying stepsand preferably at the end of same, a laying space corresponding to thespace taken up by a single strip-like element laid down.

Preferably, the step of applying said strip-like elements by means ofsaid first laying unit and said second laying unit takes place byapplication of said strip-like elements in pairs.

Preferably, said step of calculating said whole number of strip-likeelements is carried out by dividing the extension of the radiallyexternal laying surface by the amount (W-S)/sin γ, and approximating theresult to the closest whole number.

Preferably, said path is an arc of a circumference coaxial with thegeometric rotation axis.

Still more preferably, shifting of the first laying unit—along said arcof a circumference subtends a predetermined angle measured with respectto a diametrical direction passing through the second laying unit.

Shifting along a circumference coaxial with the forming drum enables thelaying unit to be always maintained to such a distance from the drumsurface that a correct laying of the strip-like elements is allowed.

Preferably, rotation of the forming drum around the geometric rotationaxis thereof is carried out by steps, each step corresponding to anadvancing angle of said forming drum, so that the predetermined angle isabout half said advancing angle.

Preferably, the predetermined angle is smaller than or equal to about10°.

In addition, the predetermined angle is greater than or equal to about2°.

More preferably, the predetermined angle is smaller than or equal toabout 8°.

In addition, the predetermined angle is greater than or equal to about4°.

The predetermined angle of minimum shifting of the laying unit isadapted to enable the last strip-like element to be laid down in thespace of the side surface of the drum that has been left empty.

In accordance with a preferred embodiment of the invention, applicationof the strip-like element is carried out by: —applying a plurality ofstrip-like elements in pairs in succession, the two strip-like elementsof each pair being simultaneously applied to the opposite portions ofthe radially external laying surface, the two strip-like elements ofeach pair being mutually offset relative to a diametrical directionpassing through the geometric rotation axis of the forming drum;—applying a single strip-like element on a portion of the radiallyexternal laying surface that has been left empty.

In addition, at each of the first rotation steps a pair of strip-likeelements of said plurality is applied and at a last rotation step thesingle strip-like element is applied.

In this way, it is possible to reduce the time of the work cycle to aminimum because all strip-like elements except the last one are laid inpairs, so that the required time is halved as compared with the case inwhich a single laying unit is used.

Preferably, the single strip-like element is laid down by the firstlaying unit.

Alternatively, the single strip-like element is laid down by the secondlaying unit.

In order that the unit laying the last strip-like element is that whichwas shifted, the first laying unit is moved along the path in adirection consistent with a rotation direction of the forming drum.

Alternatively, the first laying unit is moved along the path in anopposite direction relative to a rotation direction of the forming drum.

In accordance with a preferred embodiment of the invention, duringapplication of each strip-like element, a relative angular rotation iscarried out between the strip-like element and the forming drum around acorrection axis that is substantially radial to the geometric rotationaxis.

In addition, angular rotation around the correction axis is carried outin a progressive manner during application of the strip-like element.

It is therefore possible to lay down angled strip-like elements therebyensuring a perfect structural homogeneity of the carcass ply.

According to an embodiment, the strip-like elements are applied inmutually approached relationship.

Preferably, the strip-like elements are applied in partly overlappedrelationship with each other, so as to ensure continuity of the carcassstructure also after radial expansion, as required to make said carcassstructure adhere against the inner surface of the outer sleeve.

In accordance with a preferred embodiment of the invention, the processcomprises the step of moving the forming drum forward along a transportline between subsequent work stations; wherein in order to apply said atleast one carcass ply around said at least one radially externalsurface, said forming drum is picked up from the transport line andlocated between the first and second laying units; and wherein afterapplication of said at least one carcass ply, said forming drum is putback on the transport line.

According to an embodiment, said radially external surface is theradially external surface exhibited by tyre components already laid downon said forming drum. This is, for instance, the case in which thecarcass ply is build on a previously applied liner. Preferably saidwidth of the overlapped part S is greater than or equal to about 1 mm.

Preferably said width of the overlapped part S is smaller than or equalto about 2.5 mm.

Preferably said ply angle γ is greater than or equal to about 60°.

Preferably said ply angle γ is smaller than or equal to about 90°.

Preferably, after the step of calculating the whole number of strip-likeelements to be applied, a true width S_(e) of the overlapped part iscalculated.

Playing on the width variation of the overlapped part it is possible tocorrectly lay down the strip-like elements with a constant pitch.

Preferably, the width W of the strip-like elements is greater than orequal to about 20 mm.

In addition, preferably, the width W of the strip-like elements issmaller than or equal to about 40 mm.

More preferably, the width W of the strip-like elements is greater thanor equal to about 25 mm.

More preferably, the width W of the strip-like elements is smaller thanor equal to about 35 mm.

As already mentioned, use of strip-like elements of such a width allowsthe time for a work cycle to be contained within limits.

Preferably, said first laying unit and second laying unit are adapted toapply pairs of strip-like elements.

Preferably, said path is an arc of a circumference concentric with thegeometric rotation axis.

In accordance with a preferred embodiment, the apparatus comprises afirst auxiliary adjustment device and a second auxiliary adjustmentdevice to shift each of said first and second laying units aroundrespective correction axes that are substantially radial to thegeometric rotation axis.

These features allow laying of strip-like elements on the forming drumwith any angle relative to the circumferential extension of same.

Preferably, the apparatus comprises a bearing structure adapted to carrythe forming drum; a first frame installed on the bearing structure abovethe forming drum and carrying the first laying unit; a second frameinstalled on the bearing structure under the forming drum and carryingthe second laying unit; wherein the adjustment device is mounted betweenthe bearing structure and the first frame, to shift the first layingunit along said adjustment path.

Preferably, the adjustment device comprises a supporting plate hinged onthe bearing structure around a hinge axis coincident with the geometricrotation axis, and at least one actuator disposed between the supportingplate and the bearing structure; the first frame being installed on saidsupporting plate. The structure is compact and stiff and the apparatusis therefore able to lay down the strip-like elements in a quick andprecise manner.

In addition, preferably, the supporting plate has a C-shapedconformation delimiting a housing region adapted to receive the formingdrum.

The C-shaped conformation of the plate allows easy placement and removalof the forming drum.

Preferably, the second auxiliary adjustment device comprises: —archedguides mounted on the bearing structure and coaxial with a correctionaxis that is substantially radial to the geometric rotation axis; thesecond frame being mounted on said arched guides;

-   -   at least one actuator to move the second frame on said arched        guides.

In addition, the first auxiliary adjustment device comprises:

-   -   arched guides mounted on the supporting plate and coaxial with a        correction axis that is substantially radial to the geometric        rotation axis; the first frame being mounted on said arched        guides;    -   at least one actuator to move the first frame on said arched        guides.

The arched guides ensure an accurate movement of the frame, thismovement accuracy also having repercussions on the laying accuracy ofthe strip-like elements.

According to an embodiment, the apparatus comprises successive workstations; a transport line extending between said successive workstations; a picking-up device to shift the forming drum between thetransport line and a work region of the bearing structure positionedbetween the first and second laying units. Preferably, the picking-updevice comprises a vertically movable lifter and a horizontally movableconveyor.

This structure allows mass working operations to be carried out inseries, which gives rise to an increase in the productivity and areduction in the production costs of the tyres.

Preferably, the forming drum has a substantially cylindrical sidesurface.

In addition, the apparatus comprises at least one calculation unit tocalculate the whole number of strip-like elements to be laid down.

Preferably, said calculation unit is interfaced with a control unit forcommand of said adjustment device when an odd number of strip-likeelements is to be laid down.

It is sufficient to enter the preset design values (input data) into thecalculation unit to enable the apparatus to build the carcass ply in thecorrect manner. The work cycle therefore can be set and inputted easilyand quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become more apparent from thedetailed description of a preferred but not exclusive embodiment of aprocess and an apparatus for manufacturing tyres, in accordance with thepresent invention. This description will be set out hereinafter withreference to the accompanying drawings, given by way of non-limitingexample, in which:

FIG. 1 diagrammatically shows a top view of an apparatus formanufacturing tyres for vehicle wheels made in accordance with thepresent invention;

FIG. 2 is a perspective view of a station of the apparatus seen in FIG.1, in which a carcass ply is laid down on a forming drum;

FIG. 3 is a side view of the station shown in FIG. 2;

FIGS. 4a and 4b show diagrammatic side views of the forming drum housedin the station in FIG. 2 during respective steps of the processaccording to the-invention;

FIG. 5 is a diagrammatic front view of the forming drum seen in FIG. 3provided with a carcass ply;

FIG. 6 diagrammatically shows a laying unit for strip-like elements;

FIG. 7 is a fragmentary diametrical section view of a tyre that can bemanufactured with the process and apparatus in question.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawings, an apparatus for manufacturing tyres forvehicle wheels designed to put into practice a process according to thepresent invention has been generally identified with reference numeral1.

Apparatus 1 is designed to manufacture tyres 2 (FIG. 7) essentiallycomprising a carcass structure 2 a having at least one carcass ply 3. Alayer of airtight elastomeric material, or so-called “liner” 4, can beapplied internally of the carcass ply/plies 3. Two annular anchoringstructures 5 each comprising a so-called bead core 5 a carrying anelastomeric filler 5 b at a radially external position, are inengagement with respective end flaps 3 a of the carcass ply/plies 3. Theannular anchoring structures 5 are integrated close to regions usuallyidentified with the name of “beads” 6, at which usually engagementbetween tyre 2 and a respective mounting rim occurs.

A belt structure 7 comprising one or more belt layers 7 a. 7 b iscircumferentially applied around the carcass ply/plies 3 and a treadband 8 is circumferentially superposed on the belt structure 7.

So-called “underbelt inserts” can be associated with the belt structure7; they are each located between the carcass ply/plies 3 and one of theaxially opposite end edges of the belt structure 7. In addition, or asan alternative to the underbelt inserts 9, annular inserts (not shown)of elastomeric material and/or comprising textile or metallic cordssubstantially parallel to the circumferential extension direction of thetyre (0-degree belt layer) or other reinforcing elements can be radiallysuperposed at least on the axially opposite end edge of the belt layers7 a, 7 b and/or interposed between the belt layers 7 a, 7 b themselvesat least at said end edges.

Two sidewalls 10 each extending from the corresponding bead 6 to acorresponding side edge of the tread band 8, are applied at laterallyopposite positions to the carcass ply/plies 3.

Apparatus 1 comprises a forming drum 11 on which at least part of thecomponents designed to form the carcass structure 2 a of tyre 2 is builtand/or assembled. The forming drum 11 can consist either of a firststage building drum if apparatus 1 is designed to carry out a buildingprocess of the so-called “two-stage” type, or of a building drum of thetype usually referred to as “unistage” if a unistage building process iswished to be carried out.

In more detail, the forming drum 11 lends itself to first receive thepossible liner 4 and subsequently the carcass ply or plies 3, so as toform a cylindrical carcass sleeve.

Devices not shown coaxially engage one of the annular anchoringstructures 5 around each of the end flaps 3 a by positioning an outersleeve comprising the belt structure 7 and tread band 8 to a coaxiallycentred position around the cylindrical carcass sleeve and shaping thecarcass sleeve into a toroidal configuration through radial expansion ofthe carcass ply, so as to cause application thereof against a radiallyinternal surface of the outer sleeve.

Tyre 2 thus built lends itself to be submitted to a vulcanisationtreatment and/or other working operations provided in the work cycle.

According to the present invention, it is provided that during buildingof tyre 2, said at least one carcass ply 3 be made by means of buildingdevices 12 designed to apply a plurality of strip-like elements 13 inmutual circumferential contact relationship onto the forming drum 11, soas to form at least one ply layer having a continuous circumferentialextension around the geometric axis “X-X” of said forming drum 11. Theforming drum 11 has a radially external laying surface 14 that issubstantially cylindrical.

The building devices 12 are placed in a laying station 15, shown inFIGS. 1, 2 and 3, which in the preferred embodiment comprises a bearingstructure 16 consisting of a lattice of tubes.

The bearing structure 16 delimits a seat in which the forming drum 11 ispositioned and supported in a rotatable manner around its geometric axis“X-X”. Devices 17, in the form of a mandrel driven by a motor forexample, serve to set the forming drum 11 in rotation around saidgeometric axis “X-X”.

A first laying unit 18 and a second laying unit 19 are mounted on thebearing structure 16 close to mutually opposite portions of the formingdrum 11 and are adapted to apply the strip-like elements 13 onto saidforming drum 11 during rotation of the latter.

Preferably, the forming drum 11 is rotated by steps and after eachrotation step, the laying units 18, 19 each simultaneously apply astrip-like element 13.

Apparatus 1 further comprises two feeding units 20, each designed tosupply the strip-like elements 13 of predetermined length, preferablyone by one, to the respective laying unit 18, 19. For the sake ofsimplicity, FIG. 6 only shows the feeding unit 20 interlocked with thefirst laying unit 18.

The strip-like elements 13 are obtained by cutting operationssequentially carried out on at least one continuous strip element 21coming from an extrusion and/or calendering device, or from a feed reeland therefore all have the same width “W”. Preferably, this width “W” isincluded between about 20 mm and about 40 mm.

The continuous strip element 21, and consequently the strip-likeelements 13 obtained therefrom, each have a plurality of cords orsimilar thread elements of metallic or textile material, extendingparallel to each other along the longitudinal extension of thecontinuous strip element and the strip-like element itself, and at leastpartly coated with a layer of elastomeric material applied by anextrusion and/or calendering operation.

The laying units 18, 19 and feeding units 20 are of the type for exampledescribed in the International Patent Application WO2006IB002070 in thename of the same Applicant.

In particular, each feeding unit 20 comprises at least one cuttingmember 22 designed to cut the continuous strip element 21perpendicularly or according to a predetermined inclination relative tothe longitudinal extension of same, to obtain the individual strip-likeelements 13.

Combined with the cutting member 22 is at least one grip member 23movable between a first work position at which it is adapted to engage afinal end of the continuous strip element 21 close to the cutting member22, and a second work position at which it is spaced apart from thecutting member 22 itself.

Following translation from the first to the second work positions, thegrip member 23 drags along the continuous strip element 21 so as tostretch it out beyond the cutting member 22 and preferably at a positionradially close to the forming drum 11, according to a segment of alength corresponding to that of the strip-like element 13 to be obtainedfollowing subsequent operation of the cutting member 22. In theaccompanying figures, a pair of guide rollers operating on thecontinuous strip element 21 at a region immediately upstream of thecutting member 22 is identified with 24.

Each of the laying units 18, 19 lends itself to sequentially engage eachof the strip-like elements 13 prepared in the previously describedmanner, to determine application of same onto the radially externallaying surface 14 exhibited by the forming drum 11.

In this regard, it should be pointed out that said radially externalsurface 14 can be either the radially external surface belonging to theforming drum 14 or, preferably, the radially external surface belongingto components of tyre 2 already laid on said forming drum 11, such asliner 4 for example.

Each of the laying units 18, 19 comprises at least one presser element25 movable along the strip-like element 13, in a contrast relationshipagainst the radially external surface 14 of the forming drum 11.

In more detail, in a preferred embodiment, use of at least two presserelements 25 is provided, each of them being carried by a support element26 movable along a guide structure 27 upon the action oftransverse-movement devices, of the worm screw type for example, notshown as they can be made in any manner convenient for a person skilledin the art.

Also preferably in engagement with each support element 26 is at leastone auxiliary retaining element 28 adapted to co-operate with therespective presser element 25 to retain the strip-like element 13 at theinstants elapsing between cutting of said strip-like element upon theaction of the cutting unit 22 and application of same onto the formingdrum 11.

In more detail, each auxiliary retaining element 28 can consist of asmall plate (or other similar mechanical element) projecting from therespective support element 26 so as to offer a supporting seat for thecontinuous strip element 21 dragged along by the grip member 23 and forthe cut strip-like element 13.

Associated with each of the laying units 18, 19 are radial-movementdevices designed to move the presser elements 25 radially close to theradially external surface 14 of the forming drum 11. Theseradial-movement devices are not shown or described in detail as they canbe made in any manner convenient for a person skilled in the art, andcan operate on the guide structure 27 for example, and/or directly onthe presser elements 25, in order to bring the strip-like element 13 incontact relationship on the radially external surface 14.

Also provided are transverse-movement devices, not shown too, as theycan be made in any convenient manner, and operating between the guidestructure 27 and the support elements 26 for example, to move thepresser elements 25 between a first operating condition at which theyare disposed mutually close and a second operating condition at whichthey are spaced apart relative to a transverse symmetry plane of theforming drum 11.

In the embodiment shown, the first and second laying units 18, 19 areinstalled on respective first and second frames 29, 30, mounted on thebearing structure 16. In more detail, the guide structure 27 of each ofthe laying units 18, 19 is connected to and supported by the respectiveframe 29, 30, which has a lattice structure surrounding the laying unit18, 19 itself. When the bearing structure 16 is correctly installed withits base 31 resting on the ground, the first and second frames 29, 30lie one upon the other substantially aligned along a vertical direction.

The seat in which the forming drum 11 is housed remains interposedbetween the first and second laying units 18, 19, and said two layingunits 18, 19 face up towards the portions of the forming drum 11 lyingon substantially opposite sides relative to the geometric axis “X-X”.

According to a preferred embodiment, the first laying unit 18 is locatedover the forming drum 11 and the second laying unit 19 is located underthe forming drum 11.

The bearing structure 16 therefore defines a sort of cage inside whichthe laying units 18, 19 and forming drum 11 are housed.

Apparatus 1 further comprises an adjustment device 32 entrusted with thetask of shifting one of the laying units 18, 19 along an adjustment path“C-C” lying in a plane orthogonal to the geometric rotation axis “X-X”of the forming drum 11 and being substantially arced about the radiallyexternal laying surface 14 exhibited by the forming drum 11. Preferably,path “C-C” is an arc of a circumference coaxial with said geometricrotation axis “X-X” (FIGS. 4a and 4b ).

In the non-limiting embodiment shown, the adjustment device 32 ismounted between the bearing structure 16 and the first frame 29 andtherefore allows adjustment of the position of the first laying unit 18along said path “C-C”, so as to lay down the strip-like elements 13 inan even or odd number, as shown in the following.

In detail, the first frame 29 is installed on a supporting plate 33which in turn is movable on the bearing structure 16 around an axiscoincident with the geometric rotation axis “X-X” of the forming drum11.

In the embodiment shown, the supporting plate 33 is hinged around saidgeometric rotation axis “X-X” and an actuator 34 spaced apart from thisaxis “X-X” causes rotational movement of same.

The supporting plate 33 further has an opening defining a housing regionin which the forming drum 11 is accommodated, so that the first layingunit 18 can operate on the radially external surface 14 from the top.

Preferably, said housing region, as shown, is delimited by a C-shapedoutline of the supporting plate 33 which is open towards a picking up’device 35 that, as illustrated in the following, enables the formingdrum 11 to be easily put down into the seat or removed therefrom.

The second frame 30 is mounted on the base 31 of the bearing structure16 and the second laying unit 19 operates on the radially externalsurface 14 of the forming drum 11 from below.

Apparatus 1 further comprises a first auxiliary adjustment device 36 anda second auxiliary adjustment device 37 capable of shifting each of saidfirst and second laying units 18, 19 around respective correction axes“Y-Y”, “Y′-Y′” that are substantially radial to the geometric rotationaxis “X-X”.

The auxiliary adjustment devices 36, 37 have the function of laying thestrip-like elements 13 on the forming drum 11 with any angle relative tothe circumferential extension of same, so as to make carcass plies inwhich the cords being part thereof have a ply angle γ different from 90°(FIG. 5) relative to a longitudinal extension direction of the ply, i.e.relative to a circumferential direction of the tyre to be made.

As illustrated, the first auxiliary adjustment device 36 comprises twoarched guides 38 mounted on an upper face of the supporting plate 33 andcoaxial with the respective correction axis “Y-Y”. The first frame 29 ismounted by means of runners 39 on these arched guides 38 and an’actuator, not shown, enables said first frame 29 to be moved on saidarched guides 38 around the respective correction axis “Y-Y”. Likewise,the second auxiliary adjustment device 37 comprises two arched guides 40mounted on the base 31 of the bearing structure 16 and coaxial with therespective correction axis “Y1-Y1”. The second frame 30 is mounted bymeans of runners 41 on said arched guides 40 and an actuator, not shown,enables said second frame 30 to be moved on said arched guides 40 aroundthe respective correction axis “Y′-Y′”.

Each of the auxiliary adjustment devices 36, 37 allows a rotation of thelaying units 18, 19 around the respective correction axes “Y-Y”, “γ′-γ′”according to a rotation angle of about 60°, i.e. of about +/−30°relative to a direction parallel to the geometric rotation axis “X-X”.

Preferably, apparatus 1 according to the invention comprises a pluralityof work stations “WS” (diagrammatically shown in FIG. 1); among whichthe laying station 15, at each of which one or more of the abovementioned operations for manufacturing tyre 2 are carried out. Forinstance, —in a station placed before the laying station 15, liner 4 isapplied onto the forming drum 11. In a station placed after the layingstation 15, the annular anchoring structures 5 are associated with thecarcass ply 3.

A transport line 42 extends between said work stations “WS” and is usedto shift the forming drum 11 between one station “WS” and the subsequentone.

The above mentioned picking up device 35 is used to pick up the formingdrum 11 from the transport line 42 and position it into the seat of thebearing structure 16 where it is engaged by the mandrel and, once thestrip-like elements 13 have been applied, to bring the drum 11 back onthe transport line 42. In the embodiment shown, the picking up device 35comprises a lifter 43 moved by motors not shown along a vertical guide44. Lifter 43 comprises a pair of arms 45 having grip ends 46 adapted toengage pins 47 of the forming drum 11 coaxial with the geometricrotation axis “X-X”. Arms 45 are movable between a lower position and araised position in which they substantially lie at the same height asthe mandrel of the bearing structure 16.

The picking up device 35 further comprises a conveyor 48 moved by motorsnot shown along a horizontal guide 49. Conveyor 48 comprises a pair ofarms 50 substantially placed at the same height as the mandrel of thebearing structure 16 and having catching clamps 51 adapted to engage thepins 47 of the forming drum 11. Arms 50 are movable between a firstposition at which they lie spaced apart from the bearing structure 16and substantially over the transport line 42, and a second position atwhich they lie close to the mandrel in the bearing structure 16.

Lifter 43 carries drum 1 in the raised position where conveyor 48 picksit up and brings it as far as into the seat of the bearing structure 16.Once the forming drum 11 is positioned in the seat of the bearingstructure 16 and associated with the mandrel, the position of thesupporting plate 33 is adjusted in such a manner as to shift, ifnecessary, the first laying unit 18 along the arc of a circumference“C-C” and apply the strip-like elements 13 in the correct manner arounddrum 11.

In particular, shifting of the first laying unit 18 along the arc of acircumference “C-C” subtends a predetermined angle “α” measured relativeto a diametrical vertical direction “d” passing through the secondlaying unit 19, the value of said predetermined angle “α” beingcalculated starting from the tyre fitting, the width ‘W’ of thestrip-like elements 13, the ply angle “γ” and the possible width of theoverlapped part “S” between adjacent strip-like elements 13.

The width “W” of the strip-like elements 13, measured transversely ofthe longitudinal extension of the strip-like element 13, is preferablyincluded between about 20 mm and about 40 mm, more preferably betweenabout 25 mm and about 35 mm.

In fact, according to an embodiment of the process, the strip-likeelements 13 are mutually approached along the circumferential extensionof drum 11.

According to a preferred variant of the process, the strip-like elements13 on the contrary partly overlap each other. Under this situation, itis defined as the width of the overlapped part “S” the extension of theoverlapped-part region between two adjacent strip-like elements 13measured along the circumferential extension of the forming drum 11.

This width of the overlapped part “S” is preferably included betweenabout 1 mm and 2.5 mm, more preferably included between about 1.5 mm and2 mm.

In more detail, the circumferential extension of drum

11 and the circumferential ‘extension of the radially external surface14 corresponding to the extension of the carcass ply 3 are calculatedfrom the fitting diameter and from the thickness of liner 4, if any, orof possible other components to be previously laid on the forming drum11.

The width “W” of the strip-like elements 13 and the ply angle “γ” beingknown, and given the width of the overlapped part “S”, a theoreticalpitch of the strip-like elements 13 is calculated along the extension ofdrum 11. The theoretical pitch is equal to the difference between thewidth “W” of the strip-like elements 13 and the width of the overlappedpart “S” divided by the sine of the ply angle “γ”.

Calculated from the theoretical pitch is the number of strip-likeelements 13 necessary to have that theoretical pitch, as the ratio ofthe circumferential extension of ply 3, liner 4 being taken intoaccount, to the theoretical pitch, and this number is approximated tothe closest integer or whole number

In particular, if the difference between the calculated number and itswhole part is smaller than or equal to 0.5, approximation to the lowerinteger “n” is done. If the difference between the calculated number andits whole part is greater than or equal to 0.51 approximation to thehigher integer “n” is done.

The whole number of strip-like elements 13 being known, the true pitch“P_(e)” of the strip-like elements 13 is calculated and, since the width“W” of the strip-like elements 13 is fixed, the true width of theoverlapped part “S_(e)”. The true pitch “P_(e)” is equal to the ratiobetween the circumferential extension of the ply and the whole number“n”. The true width of the overlapped part “S_(e)” is equal to thedifference between the width “W” of the strip-like elements 13 and thetrue pitch “P_(e)” multiplied by the sine of the ply angle “γ”.

Being the number of the strip-like elements 13 known, it is furthercalculated the advancing angle “β” that the forming drum 11 must coverat each rotation step, as the ratio between the round angle and thewhole number “n”.

If the whole number “n” of strip-like elements 13 to be laid down is aneven number, the first laying unit 18 is positioned exactly on thevertical diametrical direction “d” passing through the second layingunit 19, i.e. exactly facing the second laying unit 19. Under thissituation the predetermined angle “α” as above defined is equal to zero.

The first laying unit 18 being thus positioned, the forming drum 11 ismoved forward by steps and at each step the two laying units 18, 19apply two strip-like elements 13.

The two units 18, 19 apply the same number of strip-like elements 13corresponding to half the whole number “n” and each unit 18, 19 appliesthe strip-like elements on an arc of 180°.

In addition, during laying of the strip-like elements 13 a relativeangular rotation is carried out between the strip-like elements 13 andthe forming drum 11 by rotation of the first and second frames 29, 30around the respective correction axes “Y-Y”, “Y′-Y′”, preferably in aprogressive manner during laying of the strip-like elements 13themselves, so as to obtain the ply angle “γ”.

If the whole number “n” of strip-like elements 13 to be laid down is anodd number, the first laying unit 18 is positioned in such a manner thatthe predetermined angle “α” is equal to about half the advancing angle“β” (FIGS. 4a and 4b ).

This predetermined angle “α” is preferably included between about 2° andabout 10° and more preferably between about 4° and about 8°.

The first laying unit 18 being thus positioned, the forming drum 11 ismoved forward by steps and at each of the first rotation steps the twolaying units 18, 19 apply a pair of strip-like elements 13 each time.

Due to the mutual position of the two laying units 18, 19, the twostrip-like elements—13 of the pair are mutually offset relative to adiametrical direction passing through the geometric rotation axis.

Therefore an empty portion remains where a single strip-like element 13is to be ̂ applied in register with a last rotation step, whichstrip-like element is applied by one alone of the laying units 18, 19while the other is idle (FIG. 4b ).

In accordance with an embodiment of the process shown in FIGS. 4a and 4b, the first laying unit 18 is shifted along the path “C-C” in adirection consistent with a rotation direction “V” of the forming drum11.

Under this situation, the single strip-like element 13 is laid last bythe first laying unit 18.

In accordance with an alternative embodiment of the process, the firstlaying unit 18 is shifted along the path “C-C” in an opposite directionrelative to the rotation direction “V” of the forming drum 11.

Under this situation, the single strip-like element 13 is laid last bythe second laying unit 19.

Preferably, apparatus 1 further comprises a control unit, not shown,which is interfaced with a calculation unit capable of carrying out theabove mentioned calculations based on the input data (fitting diameterof drum 11, radial thickness of the components laid on the drum prior tothe carcass ply/plies 3, width “W” of the strip-like elements 13, plyangle “γ” and width of the overlapped part “S”) entered by an operator,and by means of devices capable of automatically operating at least theadjustment device 32 to shift the first laying unit 18 based on thecalculated data.

1-50. (canceled)
 51. An apparatus for manufacturing tyres for vehiclewheels, each tyre comprising a carcass structure including at least onecarcass ply, a tread band at a radially external position to saidcarcass structure and a belt structure interposed between said carcassstructure and tread band, the tyres being manufactured including tyrescomprising carcass plies made by laying down an even whole number ofstrip-like elements and tyres comprising carcass plies made by layingdown an odd whole number of strip-like elements, comprising: a formingdrum having at least one radially external laying surface; devices forbuilding at least one carcass ply around said radially external surface,said at least one carcass ply having axially opposite end flaps; anddevices for coaxially engaging an annular anchoring structure aroundeach of the end flaps, wherein the devices for building at least onecarcass ply around said radially external surface comprise: devices forsetting the forming drum in rotation around a geometric rotation axisthereof; a first laying unit and a second laying unit mounted atmutually opposite portions of the forming drum and capable of beingadapted to apply a plurality of strip-like elements along thecircumferential extension of the forming drum; an adjustment device forshifting the first laying unit along an arced adjustment path which liesin a plane orthogonal to the geometric rotation axis, the arcedadjustment path being an arc of a circumference coaxial with thegeometric rotation axis for applying a single strip-like element. 52.The apparatus as claimed in claim 51, wherein said first laying unit andsecond laying unit are capable of being adapted to apply pairs ofstrip-like elements.
 53. The apparatus as claimed in claim 51,comprising a first auxiliary adjustment device and a second auxiliaryadjustment device to shift each of said first and second laying unitsaround respective correction axes that are substantially radial to thegeometric rotation axis.
 54. The apparatus as claimed in claim 51,comprising: a bearing structure capable of being adapted to carry theforming drum; a first frame installed on the bearing structure above theforming drum and carrying the first laying unit; and a second frameinstalled on the bearing structure under the forming drum and carryingthe second laying unit, wherein the adjustment device is mounted betweenthe bearing structure and the first frame to shift the first laying unitalong said adjustment path.
 55. The apparatus as claimed in claim 54,wherein the adjustment device comprises a supporting plate hinged on thebearing structure around a hinge axis coincident with the geometricrotation axis and at least one actuator disposed between the supportingplate and the bearing structure, the first frame being installed on saidsupporting plate.
 56. The apparatus as claimed in claim 55, wherein thesupporting plate has a C-shaped conformation delimiting a housing regioncapable of being adapted to receive the forming drum.
 57. The apparatusas claimed in claim 54, comprising a first auxiliary adjustment deviceand a second auxiliary adjustment device to shift each of said first andsecond laying units around respective correction axes that aresubstantially radial to the geometric rotation axis, wherein the secondauxiliary adjustment device comprises: arched guides mounted on thebearing structure and coaxial with a correction axis that issubstantially radial to the geometric rotation axis, the second framebeing mounted on said arched guides; and at least one actuator to movethe second frame on said arched guides.
 58. The apparatus as claimed inclaim 54, comprising a first auxiliary adjustment device and a secondauxiliary adjustment device to shift each of said first and secondlaying units around respective correction axes that are substantiallyradial to the geometric rotation axis, wherein the first auxiliaryadjustment device comprises: arched guides mounted on the supportingplate and coaxial with a correction axis that is substantially radial tothe geometric rotation axis, the first frame being mounted on saidarched guides; and at least one actuator to move the first frame on saidarched guides.
 59. The apparatus as claimed in claim 55, comprisingsuccessive work stations; a transport line extending between saidsuccessive work stations; a picking-up device to shift the forming drumbetween the transport line and a work region of the bearing structurepositioned between the first and second laying units.
 60. The apparatusas claimed in claim 59, wherein the picking-up device comprises avertically movable lifter and a horizontally movable conveyor.
 61. Theapparatus as claimed in claim 51, wherein the forming drum has asubstantially cylindrical side surface.
 62. The apparatus as claimed inclaim 51, comprising at least one calculation unit to calculate a wholenumber of strip-like elements to be laid down.
 63. The apparatus asclaimed in claim 62, wherein said calculation unit is interfaced with acontrol unit for command of said adjustment device when an odd number ofstrip-like elements is to be laid down.